Ukrainian riot troops block a Kiev street during a gathering of supporters of EU integration.

Reuters: Valentyn Ogirenko

Ukraine's president has backed a call for talks with the opposition to end weeks of protests in Kiev, but tensions remain high as pro-Europe demonstrators barricaded their protest camp in preparation for police raids.

Viktor Yanukovich's call, made via the presidential website, comes after weeks of angry demonstrations over the country's decision to refuse a trade pact with Europe in favour of closer ties with Russia.

As riot police took up new positions in the capital, the main opposition spokesman, Vitaly Klitschko, called on the protesters to stand their ground and warned Mr Yanukovich that he would have blood on his hands if security forces tried to end the stand-off violently.

Mr Klitschko, a former heavyweight boxing champion who has entered politics, later tweeted that some protest barricades were being taken down by police in a southern part of the city.

Across town, police dismantled tents to free the main road near the government headquarters and herded protesters back, but no clashes were reported and there were no attempts by police to move against the large encampment of protesters on Kiev's Independence Square, a focal point of the demonstration.

Meanwhile, masked men with guns raided the party headquarters of jailed opposition leader Yulia Tymoshenko and took a computer server, a spokeswoman said.

Ukraine's Interior Ministry said the search was sanctioned by the courts.

With pressure growing on a shaky economy, the presidential website said Mr Yanukovich supported a proposal for round-table talks involving the authorities and the opposition as a possible "platform for mutual understanding".

No date was given for when the reconciliation talks could be held, nor was it clear what the opposition's reaction to Mr Yanukovich's proposal would be.

However, it was the first real sign by Mr Yanukovich, whose switch in trade policy away from the EU towards Russia on November 21 provoked the unrest, that he might be ready to listen to opposition demands for the resignation of his government and early elections.

Opposition says blood will be on president's hands

Despite Mr Yanukovich's words, tension rose sharply on the streets after riot police units moved to take up their positions at potential flashpoints.

On Monday (local time), demonstrators responding to calls from opposition leaders threw up new blocks in streets blanketed by snow to seal off their main protest camp on Independence Square.

"We call on people to stand their ground, and peacefully, without using force or aggression, to defend their right to live in a free country," said Mr Klitschko, who is increasingly being seen as a national leader-in-waiting.

Although neither side has given a detailed account of what was agreed at the talks, Ukrainian prime minister Mykola Azarov says a "big agreement" was reached.

Though most people believe Mr Putin may have offered credits and a cheaper price for gas in return for dumping a European Union trade pact, the secrecy surrounding the talks has only fuelled opposition suspicions that Mr Yanukovich might be readying to take Ukraine into a Moscow-led customs union.

EU, US call on Kiev to show restraint

The president of the EU commission, Jose Manuel Barroso, has urged the Ukraine government to show restraint amid the biggest street protests since the 2004 Orange Revolution, when people power forced a re-run of a fraud-tainted election and thwarted Mr Yanukovich's first run for the presidency.